Accession Number : ADA317979

Title :   Characterization of Cryogenic Solid Hybrid Rocket Motors.

Descriptive Note : Technical paper,

Corporate Author : PHILLIPS LAB EDWARDS AFB CA

Personal Author(s) : Carrick, Patrick G. ; Larson, C. W. ; Pfeil, Kevin L.

Report Date : DEC 1995

Pagination or Media Count : 12

Abstract : The study of the combustion of cryogenic (77K) solid hydrocarbons in a laboratory scale tube burner that approximates the geometry of the hybrid rocket was extended. This work was carried out to demonstrate the feasibility of cryogenic fuel combustion in the hybrid rocket geometry and to extend knowledge about hybrid rockets to fuels that have very high regression rates as a consequence of their high mass transfer number, or blowing coefficient. Liquid n-pentane was condensed inside a 1-inch diameter tube that was cooled by liquid nitrogen. A mandrel was used to shape a 6-inch long by 1-inch diameter solid fuel grain with a one-half-inch diameter channel along the centerline; the mass of the n-pentane fuel grain was around 35 grams. These fuel samples were ignited with a methane/oxygen microtorch and burned with gaseous oxygen (GOX, up to 25 grams/sec) under conditions of choked flow. Combustion pressure (Pc, up to 250 psia) depends on the throat area of the choke, a converging sonic nozzle. Pc also depends on the fuel, the mass flow rates of fuel and GOX, and the 'oxidation efficiency.' Burn times varied between 1 and 8 seconds. Images of the turbulent reacting boundary layer and burning fuel surface and of the exit plume were recorded with a CCD/video system. Two figures of merit were determined: the instantaneous fuel regression rate (r'(t) cm/sec) and the instantaneous characteristic velocity (c(solid star)(t) cm/sec, the metric of 'combustion efficiency') achieved during combustion. Lower pressure experiments burned with a low oxidizer to fuel mass ratio (O/F around unity) and considerable sooting; these large r' burns were accompanied by low C(solid star) combustion efficiency, as low as 50% of C(solid star)ideal.

Descriptors :   *HYBRID ROCKET ENGINES, RATIOS, SOOT, HIGH RATE, MASS, RATES, EFFICIENCY, BOUNDARY LAYER, LOW PRESSURE, SOLIDS, COOLING, GASES, REGRESSION ANALYSIS, SURFACES, OXYGEN, COMBUSTION, FUELS, MASS FLOW, FLOW RATE, SCALE, COEFFICIENTS, HYDROCARBONS, MASS TRANSFER, SAMPLING, PRESSURE, GEOMETRY, OXIDIZERS, LABORATORIES, PLUMES, METHANE, LIQUID NITROGEN, VIDEO SIGNALS, EXITS, CRYOGENICS, FIGURE OF MERIT, STARS, BURNERS, TUBES, THROAT, BLOWERS, MASS NUMBER.

Subject Categories : Rockets

Distribution Statement : APPROVED FOR PUBLIC RELEASE